NATIONAL RADIO ASTRONOMY OBSERVATORY ARCHIVES

Papers of Woodruff T. Sullivan III: Tapes Series

Note: The interview listed below was either transcribed as part of Sullivan's research for his book, Cosmic Noise: A History of Early Radio Astronomy (Cambridge University Press, 2009) or was transcribed in the NRAO Archives by Sierra Smith in 2012-2013. The transcription may have been read and edited for clarity by Sullivan, and may have also been read and edited by the interviewee. Any notes added in the reading/editing process by Sullivan, the interviewee, or others who read the transcript have been included in brackets. If the interview was transcribed for Sullivan, the original typescript of the interview is available in the NRAO Archives. Sullivan's notes about each interview are available on the individual interviewee's Web page. During processing, full names of institutions and people were added in brackets and if especially long the interview was split into parts reflecting the sides of the original audio cassette tapes. We are grateful for the 2011 Herbert C. Pollock Award from Dudley Observatory which funded digitization of the original cassette tapes, and for a 2012 grant from American Institute of Physics, Center for the History of Physics, which funded the work of posting these interviews to the Web.

Please bear in mind that: 1) This material is a transcript of the spoken word rather than a literary product; 2) An interview must be read with the awareness that different people's memories about an event will often differ, and that memories can change with time for many reasons including subsequent experiences, interactions with others, and one's feelings about an event.

Sullivan

Ok, this is interviewing Cyril Hazard on 20 March ’73 at Groningen. You go back to the early days at Jodrell Bank, is that right?

Hazard

Not to the earliest, to late 1949. Radio astronomy was just starting then. [Alan] Maxwell and [C. Gordon] Little were doing scintillation observations. Up to then it had been mainly radar things on the moon and meteors and that sort of thing. And they were just starting up scintillation observations and I worked with them for a couple of months.

Sullivan

Using radio sources?

Hazard

Yes, Cassiopeia and Cygnus A. The 30 foot- or was it 25, no about 30 foot- radar antenna, which they used to move around by hand every hour and record the scintillations. I know I started up building a stabilized power supply for that. And [Robert] Hanbury Brown sort of arrived about the same time, started appearing, and when he finally arrived around about the end of the year or the beginning of the next year I went to work with him. Then I built the 218 foot fixed dish, had been built to do cosmic ray showers, I think. That will be in Lovell's book, I think. But it had been built to detect showers by, you know in a similar way to Arecibo, was built to do back-scatter observations. I mean it was built for the same sort of thing. And what I guess was going to be used was, probably not to transmit, it was just going to be used just as a receiver, I'm not sure. But that's what it was built for and then he [Sullivan: Hanbury Brown] suggested using it to try and detect the Andromeda Nebula because would could it tilt it over by slackening off and pulling on the guy wires. It was held up by three sets of guy wires and you could tilt it over, something like 10°. It was quite a job, actually.

Sullivan

Now when are you talking about? What year is this?

Hazard

It was about 1950. And we used to steer it off a degree or so a day by slackening off the guy wire and putting in extra bits of guy wire and tilting it over and then letting the sky go through.

Sullivan

Had there been any normal galaxies detected at this time?

Hazard

No, none had been detected, though there had been shortly after that there was some stuff in the Cambridge early survey which claimed to have detected four or five of them, but actually they're all spurious. You know M101, there was a source near M101.

Sullivan

And M51, I think they had?

Hazard

Yes, but that was something else. And M33 was actually 3C48.

Sullivan

I see, so all of those were spurious.

Hazard

They were all spurious. I don't think any of them were reliable at all. I don't think they detected anything. If you look back through the literature I think that they were all nearby sources.

Sullivan

But they were accepted at that time as being detections, were they not?

Hazard

Well, I think possibly they were.

Sullivan

They were being used as cosmological arguments as to the great argument about radio stars and saying this was the integrated effect of all the radio stars.

Hazard

They hadn't been detected at that time. I think they brought the thing out a bit later on with these things in and when M31 was the first normal one to be detected. Maybe they claimed to have detected them a little bit later on. But I know they had them in one of the things. But when we went through normal galaxies when the Mark II was built it was fairly obvious that M101 certainly wasn't detected. It was 3C295, I think. It was close to it. See that position on those was a degree or two or something like that. Just in the general neighborhood of these things. So, and M51 at 12 hours, I think. There must be another source around about it because anyhow, it's only about half a flux unit. Sorry, five flux units. So it's a pretty weak source, anyhow. I'm pretty certain that in the end we detected them, about 20 or 30 I suppose.

Sullivan

With the Mark II later?

Hazard

With the Mark II. We detected 9 or 10 with the third one, M81 although it was probably M82. It was mixed up, I think. We suspected that actually, that there was a mixture because the position was slightly off. M51 and M31. I think we probably got M101. We couldn't get down to M33. I think one or two others which were [?] where optically they were.

Sullivan

Now is this in 1950 that you're talking about?

Hazard

1950-‘51, ‘52, up to about ‘53.

Sullivan

And all with the same instrument with the guy wires?

Hazard

Yes.

Sullivan

What about M31? That was your original motivation.

Hazard

Yes, we did it about 1950 straight up. That took a little bit of time because we used to use a pen recorder which would jump off every night. It would either stop recording or jump off. I remember I slept under the bench every night to waken up when the source went through [?]. Then we did a survey of the galactic plane. We detected the broad angular-sized sources in the plane which is fairly interesting because the Cambridge people really didn't believe them because they weren't in their surveys. And I actually measured them. I left Jodrell round about then, and did my national service about 1953 or ‘54. I remember when I came back- that was what started off the measurement of the angular sizes because we suspected they were broad. And in fact they'd actually turned out when I went back and found all my old papers still in my room right where I'd left them. I'd measured all these angular sizes. I assumed they were all right just on the broadening of the beam, but we weren't too happy about it at the time. But they were all right, a couple of degrees.

Sullivan

And these were missed at Cambridge because of the interferometric...

Hazard

Because of the interferometer, yes. That was what they normally called the HB sources although it turns out that Hazard and Brown should be HBH according to the paper. As a matter of fact I did all that work. It was fairly obvious then that we had the same population that [Bernard Y.] Mills got round about the same time.

Sullivan

So Mills came up with this Class I and Class II sources?

Hazard

That's right.

Sullivan

And you agreed with this that there was a concentration in the plane?

Hazard

That's right.

Sullivan

Particularly in the extended sources?

Hazard

In the extended sources, yes. It was these bright see sources, you could see them. It was fairly conclusive. You know out of about 20 sources above a given flux, about 16 of them or whatever it was lay within a degree or so of the plane. That was fairly obvious. Then I started to look at clusters and so on at that time. The original idea was that we were trying to look at the stuff of different types and to get the ellipticals. We wanted to really get a whole group of them together. So then we started looking at Perseus and we made a boob on Perseus because we got that - Perseus and didn't spot- which we should have done, I think- that there was an odd galaxy in the cluster that was causing the trouble. So it was in the integrated flux, because we didn't have any angular size, we only had a couple of degree beam. And then we started looking for stuff in, running down through Virgo which actually is right still, although there's been a lot of objections to it because what happened was other people tried to check it in Australia by looking in the densest part of Virgo running down below 20°. And there's a problem with that in that the north galactic spur runs out and runs right dawn in the same region. The two things get all mixed up round about that point. We actually did another survey up there and we never published the results. But there is a weak stuff running right up through Virgo.

Sullivan

What frequency were you operating on?

Hazard

That early stuff was 158 megacycles. The dish was just brought up to about that point which is just open wire. Then I left Jodrell for about three years and went back about 1957.

Sullivan

Before we go on, a couple questions. Why did the Australians have a discrepancy with your result in Virgo?

Hazard

Yes, well what happens is that the thing gets - what you find out is that there is a band running down. Then you find that the band runs away from Virgo. And actually the band measured down there is actually the north galactic spur because it comes out and runs right through Virgo, crossing it round about 20°. In fact, we had a paper where we said the thing was splitting in two round about that point. So that's the north galactic spur running away from it. So you get into trouble there. So I must got back and do that again sometime and sort out that problem again. Because I never bothered to do anymore about it. But I'm sure it's right.

Sullivan

I still don't quite see what the discrepancy was? The Australians, you say, didn't realize that this was the north galactic spur?

Hazard

Nobody knew about the galactic spur at that time.

Sullivan

Ok.

Hazard

That was the thing that cropped up later on, the galactic spur cropped up a lot later on. It sort of runs up into Virgo and comes back down again. So the dish was following a big loop around the sky and people didn't realize. In fact, in those days there were lots of papers even where it formed a great circle running across the sky. And that's how, you know, we wrote the paper on it later on because when we found out it was coming back down again they had papers written on this thing in which you were sort of sitting in an arm so that the magnetic field was such that you saw the thing as a band running across. But even that presupposed it formed part of a great circle, it was in fact a small circle. And you know whether it's a supernova remnant or whether it's...

Sullivan

Just as a matter of interest, when was that?

Hazard

That was later on. That wasn't untangled until about 1957 or ‘58, something like that. It was round about that time. It was a paper we wrote in the Observatory. You know, it must have been with the Mark II, I think.

Sullivan

Well, I can check on that.

Hazard

It was- myself and Rod [Rodney D.] Davies, and somebody...

Sullivan

There's another question on your survey, you said you were had a 16 or 20 some sources were in the galactic plane. But was it an all sky survey that you did?

Hazard

No, not then. What happened was that- no, it was a strip along the galactic plane. It was this ± 10° or 15° strip. But what happened was that the amount of sky which we had within a few degrees of the plane was something like, I can't remember, 10 or 15% of the total sky. And there within sort of 90% of the strong sources lay in 20 or 30% of the area along the strip. I mean there was really no doubt about it. That was one of the things that there really was no doubt. You had these two populations.

Sullivan

No one ever did an all sky survey around this time with a dish antenna?

Hazard

There wasn't one that would do it. You see, the biggest dishes...

Sullivan

I guess with the Würzburg...

Hazard

The Würzburg was the biggest you see, until the Dutch one was built.

Sullivan

Well, no, that's not true. The 50 foot at NRL [Naval Research Laboratory] in the early ‘50s.

Hazard

Yes, you see the receivers were only going up to a few hundred megacycles. And you know, it was bad enough doing it at Jodrell with a one or two degree beam which is what we had then. But we could only go up to ±15°. So we weren't really getting terribly far because of the way the dish was fixed. And it was changed later on so that you could have a central tower which dropped down and you could put your equipment at the top. But we had to climb up 126 foot pole to put anything up there. We had to build scaffolding to get up. So you had your receiver at the bottom and so you had lots of problems such as a lot of attenuation in the cable. About 3 dB you got fluctuations in the background due to temperature changes along the cable due to mismatches. So there were problems with that.

Sullivan

What was the reason for the great height of the whole apparatus?

Hazard

Well, it was a 220 foot f/d 0.5 so you had this pole 126 foot high with your antenna at the top of it and really no way of getting up there when you were in operation. So you had to have it at the bottom. So you were losing quite a bit of sensitivity. I think if you'd had the same sort of thing nowadays with modern receivers and access to the top you'd probably pick up a reasonably good factor. Well, in fact, we did later on when we went back and redid the thing at 90 megacycles. We got loads of sources then but there was a much bigger beam.

Sullivan

Redid what?

Hazard

We did a survey again later on back at Jodrell with the fixed dish while they were getting the Mark II ready. We were playing around with confusion and so on at the time.

Sullivan

What was the period of operation of this dish?

Hazard

The dish in its original form, we certainly used it until 1949. See originally [Victor A.] Hughes was using it to do just scans across the galaxy in the zenith at and different frequencies, 70-odd megacycles, and I think 160 and 100 or something to try and get variations in the spectral index. And we took over at that point. And I think we actually started to do that originally and then we moved off and never actually did that experiment at all. We started to look at galaxies and things like that.

Sullivan

Is this the same Hughes as at Stanford now?

Hazard

Vic Hughes. He used to work on meteors before that. I think it's probably in the books about the discovery great of the great daytime meteor streams. Hughes was supposed to be turning the antenna and fell asleep, I think that's the story, I don't know whether it's true or not. But that was going up until 1954 and then I left, you see. And in the meantime while I was away they changed it to the central tower. They changed it to the central tower so you could drop it down onto another tower 20 or so feet high and you could climb up and put your equipment on the top. And they used that one for a time, when I went back. And then they started to resurface the whole thing. And I think I left again and went to Australia then and after that they never really used that one. I think they sort of stopped using it for some reason. Maybe because they were using the Mark II most of the time or maybe because they started to build no, the Mark I, it wasn't this big one, the Mark II was the small 120 foot one. And so all this stuff I've said about the Mark II is really the Mark I. And then they built the Mark II which was this elliptical thing or certainly round thing which they built on the side where these things stood anyhow. So they ended it. It must have worked on and off from 1949, certainly for five years pretty full-time. With modifications it was still working until about 1960, I suppose.

Sullivan

What about the balance between the radar astronomy and the radio astronomy? Was there any radar astronomy done besides the meteor work?

Hazard

Yes, the moon, they were trying to get lunar echoes. That was one of the big projects.

Sullivan

And how did that work out? You weren't involved in that?

Hazard

I wasn't involved. I think they got them in the end. That went on for a long time, yes, they got lunar echoes in the end. I think they got them with an array which was built there by Tom Kaiser, I think. There were quite a few people working on that. And, of course, that one has continued all the time, that one went on for a long time the stuff on the moon continued well on after the big dish was built. And, of course, then they started to use that. There was meteor which tended to separate off into upper atmospheric winds. So they were used for doing upper atmospheric winds. The scintillations were still going on. Again, they were doing upper atmospheric winds by that time. There was a lot of meteor theory going on, the development of the trails and so on. So right through the early 1950s it was largely meteors and radar work that was going on. There wasn't a great deal of radio astronomy going on because the only big instrument that we had that would do it was, in fact, the 220 foot fixed dish. And then the small thing for scintillation and a few small arrays that were built for the same sort of thing that would track sources around. I mean, things were improving, I think that the small dish had electrical drives put on it by then. You didn't have to go out every hour and move it around. No, I think that that has to be remembered in trying to assess what went on. There wasn't a great deal of equipment around really until the big dish got into operation in 1957 or so.

Sullivan

Now you say there were some arrays around and were these similar to the sort of arrays they were building at Cambridge?

Hazard

No. These arrays were all for meteors and for scintillations.

Sullivan

I see.

Hazard

Just arrays of Yagis and things like that. There was no interferometry as such going on.

Sullivan

What do you think was the reason for that?

Hazard

There wasn't anybody doing radio astronomy really.

Sullivan

Well, there were a couple of people working with the single dish doing radio astronomy.

Hazard

The big one?

Sullivan

Yes.

Hazard

Oh, yes, but that's all there were. That was enough to keep us going full-time anyhow. We used to do some interferometry. We built arrays to couple up, we could detect whether for instance Tycho's supernova, whether in fact it was similar to Cassiopeia or [?]. But you see, once we knew that these sources in the plane were resolved, then the interferometry got started. And the intensity interferometer was going on, of course, and the assumption was that these things- that they were probably of stellar dimensions and so [Roger C.] Jennison and [Mrinal] das Gupta started working on the intensity interferometer. So they were working along different lines altogether. In a certain sense, everybody else was lucky that they could resolve a lot of these sources with baselines of only a few hundred yards. Whereas the intensity interferometer was unlucky from a radio point of view that the problem was really much simpler.

Sullivan

A priori, you just didn't know what you could have...

Hazard

That's right. If it had turned out that they were all when hundredths of a second at that particular stage then, of course, it's the only one that could have done it. They could have still done Cygnus and Cassiopeia. But nobody knew that at the time. But again you see that by the time, everybody had talked about things and I think everybody knew, certainly I knew, that one could build arrays like the Mills Cross kind of thing. I mean obviously people had thought about crossing two beams and cutting the thing. But there wasn't a great deal of effort available. And because of the success obviously of the 220 foot we had gone ahead and started to build a similar type thing, a fully steerable one. A lot of effort had gone into getting that one fairly going. See I left fairly early on anyhow, in 1954.

Sullivan

I was just trying to get some feel for why Jodrell developed along mainly single dishes with some interferometry, as you say.

Hazard

Well, there was an awful lot of interferometry of course after 1954 when I wasn't there. I mean, things were just getting started. [Henry P.] Palmer and all them were going on and there was the design which I remember being worked out at lunchtime of the rotating lobe interferometer and so on. So, there actually was quite a lot going on. I don't suppose they just wanted to copy somebody else, anyhow. You've got to remember there were problems with interferometry at the time. It was really very much better than the big dishes at that time. It was losing the broad sources and running into pretty bad confusion errors which we knew about which they wouldn't believe. Actually this occurred at the time I was away, but as soon as I got back I knew they were confused. That's when [Dennis] Walsh and I started to looking at the confusion problem. And so it wasn't at all clear, I suppose anyhow, that you were doing all that much better with I think with the interferometers that you were with the big dishes. And the resolution wasn't sufficient really to resolve the sources. So that I don't think that any of the early Cambridge surveys were any better than one could have done with the dish, in fact they were inferior really. The 2C and the 3C could equally as well have been done with the dish. And, as was shown at Parkes, I mean the fact that the Parkes surveys were certainly much better than the 3C. So that once the thing had been- so that you had to build much bigger antennas for the individual interferometers and go out to much bigger spacings. So that took a fair amount of effort. And the effort at Jodrell was supposed to be going into the big dish anyhow. So it wasn't at all absolutely clear I don't think, exactly what way things were going to go in those days.

Sullivan

Ok, so you came back and you went to Australia for a while?

Hazard

Yes. What happened was when I was there the last time- I actually went back to Jodrell to work on the interferometry, to open the long baseline interferometry nominally. And I designed the antennas and so on and saw the first ones built for the long baseline interferometry. And then I sort of drifted off into doing other things again with Walsh, and by myself, and with Hanbury Brown, and so on, once the big dish came on. So I started working on different things and then started to do occultations to see if I could make them work because it was fairly obvious to me that if you really wanted to get much higher resolutions and positional accuracies it was pretty obvious that you couldn't get the accuracies and so on required without going to baselines of a mile or more. And I didn't really think anybody was going to build anything that big in those days. And it struck me that the only way of doing it was to use occultations.

Sullivan

This was in '56?

Hazard

No, this was about '57. And I did some surveys and I got a few sources I think, but the trouble was that you didn't know where any of the sources were in the sky to check them against. It was almost impossible to check what you'd got. Then 3C212 came up. And I was doing a month survey at the time. It turned out and I never published all this stuff, but we had loads of occultations over that period. But it was very difficult to interpret the records. I mean it turned out the same night that 3C212 was occulted, about four other sources were occulted. And many of them really are double and so the whole record is just a mass of jumps up and down. I wasn't entirely sure of what was going on. It was only afterwards that we could measure the positions of these sources accurately enough that I realized that these things were all occultations because one occultation can produce four jumps on the record. And with four occultations there were about 16 jumps on the record.

Sullivan

Was this the first time that radio occultations were done besides for the Sun, of course?

Hazard

There had been a look at the Crab. As far as I remember it may have been in some of the Russian things. I've got a feeling there might have been, but I've never read it. But I can't ever remember anybody really thinking about using the diffraction patterns properly and so on to deal with this properly. What happened then was that I just wanted to see if I could get the diffraction lobes and get accurate positions. I knew if you got the lobe pattern you could get the structure and so on out of it. Anyhow, we got 3C212 as I said. And we got several other ones as well which I didn't realize. I another suspected lots of them. I suspected I had another dozen or so more but I couldn't- I always intended to go through and sort it out statistically. But then I went to Australia to work on the intensity interferometer at Narrabri.

Sullivan

I wanted to ask you about the intensity interferometer, you said that Jennison was working on it at Jodrell.

Hazard

Yes, that's the radio one. That worked fine, of course, they did Cygnus.

Sullivan

I wanted to ask what was the origin of the idea? I mean in my mind anyway, you always think of Hanbury Brown with the intensity interferometer.

Hazard

That's right. It was his idea. The idea was to try and measure small angular sizes where you could really get very much bigger separations than you could get with the Michelson. And fortunately he didn't know or much optics at the time, I think, or he might not have done it. But he understood noise very well and I think he could picture in his head that you had information in the noise. In fact, if you looked at the noise ripple itself that there was information in there about the size of the source. So he could see that and he worked it out in the final theory that was worked out with [Richard Quentin] Twiss as well. And then Jennison and so on and das Gupta started building.

Sullivan

When was this that they worked out the theory?

Hazard

Oh, the theory was worked out early on, that was worked out in the early 1950s.

Sullivan

And the first application of it was Jennison?

Hazard

That's right. And he had his out-stations and he ran it for a long time. In many ways I suppose that in some ways if you look at this it really was foreshadowing aperture synthesis a long time beforehand as well because he was doing other stuff in interferometry at the time. He was messing around. And he was thinking of how to measure the phase and the amplitude at the time. And he has papers there of measuring the phase and amplitude using three spaced antennae. Once you've measured the phase you're really getting down to the aperture synthesis, really if you think about it. So I think there was a fair amount of thought going into interferometry round about then. Then he had several out there and then he started to build up the two-dimensional structure of Cygnus, of course. Then he had several out-stations round about which caused a fair amount of trouble. Because he could run for quite a long time at one of these outstations where- and I think that the thought that the out-put was looking a bit odd or something, so he went out to look at the hut and found out that somebody had gone in and removed everything from the hut and cut the main cables and just taken everything away. We just had this hut sitting there. There was nothing coming back at all. So he went on. Then he carried on with that for quite a long time, I think. Then he started to go up with satellite observations.

Sullivan

Jennison?

Hazard

Yes. He started to diverge from the mainstream. He was thinking about measuring stuff from satellites.

Sullivan

This is in the late ‘50s, I guess?

Hazard

That was in the late ‘50s I would think, yes.

Sullivan

So you say you went to Australia and worked on the stellar...

Hazard

On the stellar interferometer, yeah. I used to go down to Parkes and work there as well when there was an occultation. And the point was is that I’d given a talk on the stuff I’d done in Sydney and [Joseph L.] Pawsey and them were interested and I discussed about it and they were happy to meet at Parkes. And I went down- 273 was cropping up. By this time, you know, we had a good position. We knew there was going to be an occultation and the first one we got really was only visible for a minute or two before it went out of the field of view but we saw the diffraction lobes very strongly. So we really knew that we had to have a good go at it the next time and it was fairly obvious that we were going to get the [immersion?] but whether we were going to get the [emersion?] was a bit more dicey because we weren’t absolutely sure whether it was going to go just before, you know, or whether it was going to come out just after it got out of the field of view at the Parkes dish. You know, you can only see 60°. So there was quite a lot of modifications done to the dish particularly by Bolton by digging a hole it would go far enough down, removing safety stops, and wanted to make sure that the dish really could get to its maximum. And we got that and I think going in we got the nice diffraction pattern but coming out you could see it was double, straight off you could see the...

Sullivan

That was the first detection of its double structure?

Hazard

No, it had been known it had been double, I think, from the interferometer ones. There were two things I think which were important about this. I mean, one was that I talked to [Peter A. G.] Scheuer and so on then about looking into how to analyze and he went down to [Ronald N.] Bracewell and, of course, Scheuer worked out the thing fairly quickly. But then we did several occultations afterwards. And they were all the same, they all showed these strong diffraction lobes and double structure. And I think what was fairly obvious was that this small angular size stuff and the double structure was really extremely common. And I don't think that was at all realized how common this small stuff was. People knew there were a few sources of small angular sizes from the Jodrell stuff. But how common it was wasn't at all clear, I don't think.

Sullivan

So from this series of occultations at Parkes...

Hazard

Yes, that became fairly obvious and we knew that. [Rudolph] Minkowski was there at the time. He had a picture of the region of 3C273 from the 100" or 200" because it had been identified with a galaxy a few minutes later on and so I worked an approximate position. And you could see that it came back to this star. But you could see that this thing, the jet- I remember him saying at this time that, we knew it was in that region and that it would be very interesting if it was an edge-on galaxy because we didn't know what the jet was, because it would be the first time that it had ever been identified with an edge-on one. But we didn't get the actual position until a little bit later on, I think.

Sullivan

Sorry, but what had been identified with an edge-on?

Hazard

Any radio source.

Sullivan

You hadn't seen [?].

Hazard

That was a tiny weak source, a normal galaxy. It didn't really count as a strong source. It wasn't a real distant one, you know a real radio galaxy. Not just an ordinary spiral radiation. So it became and then it was fairly obvious I think when I looked at a lot of plates afterwards, that about 20 or 30% of these things must be that type object. I think that what always strikes me is the way in fact they tend to distort the history round about this point. You know, as though the Jodrell Bank measurements led to the discovery of quasars. You know I don't go along with that at all. We knew nothing about what was going on very much on these small angular size things. Certainly somebody identified these things with stellar objects, but they did think they were stars. You know, 3C273 came up with nothing to do with anything except it happened to be the first good occultation we got with diffraction lobes and it had the Balmer series. And then you could go back and look at 3C48 and so on and know what they were because they in fact had written all this in a paper which had gone in and then they altered it all, of course.

Sullivan

Now, what is this?

Hazard

[Allan R.] Sandage and [Thomas A.] Matthews had written a paper on 3C48 and so on saying they were stars. And, of course, they added an appendix to all this and tacked on a paper in Nature at the same time that our stuff was going out on 3C273. They really knew nothing about this until 3C273 turned up. So it's really like pulsars in a sense, it was just a pure accident.

Sullivan

I haven't looked at that paper for a while. I remember reading about it five years ago. You were saying that Sandage and Matthews had a paper saying 3C48 was a star?

Hazard

Yes.

Sullivan

And that appeared in ApJ [Astrophysical Journal]?

Hazard

Yes. And they added an appendix to say that 3C273 had been discovered to be a high redshift object. And then they redid the consequences in that section assuming now that it was a high redshift object. So they added an appendix to that paper.

Sullivan

But how did they have the lines identified?

Hazard

They didn't.

Sullivan

Oh, they just- a star without identifiable lines?

Hazard

They didn't know what they were at that time. You see they were just talking about the spectrum. And then Greenstein, I think, added a paper in at the same time as we did 3C273 because as soon as we got 3C273 you see the Balmer lines which really gave the game away. Because then you could identify the other lines, Mg II and so on was there and then you could look and see Mg II and the other ones and so that gave you a line onto the other ones. And then the whole thing started to fall into place.

Sullivan

But it was Sandage that saw the pattern?

Hazard

No, [Maarten] Schmidt.

Sullivan

Oh, Schmidt, yes, of course, saw the pattern in 3C273.

Hazard

Yes. But you see, the whole thing was really- it happened that the first one that we really got a cracking good occultation on. It was a very strong radio source which with all the diffraction lines you'd get all the positions. It also happened it was so bright at 13th magnitude you'd get all the lines out quite easily.

Sullivan

It was just an accident?

Hazard

It was just an accident, I mean, just like that. It wouldn't have mattered if you hadn't have known one single thing about anything up to that point. Everything would have fallen out on that object anyhow, and nothing else was relevant at that point. But the other stuff would have led to it in the end. But this really short-circuited the whole business. I've no doubt that if people had continued with the theory of neutron stars long enough. I mean [Franco] Pacini was already predicting radio frequency radiation. If somebody just said well, they might pulse, somebody might have started looking for pulsars and would have found them.

Sullivan

Yes, just a matter of which comes first.

Hazard

It's just a matter of how it comes first. I mean the thing just comes out "bang" by some accident.

Sullivan

Well now before the discovery of pulsars or quasars, the "discovery" or the recognition as quasi-stellar objects, was it noticed that many radio sources seemed to be associated with rare blue objects? Or was this only afterwards?

Hazard

No, no. That was only afterwards. The fact that they were blue only came out afterwards. It all started to follow on fairly quickly.

Sullivan

But the only reason an analysis was done of the spectrum for 3C48, I guess... Well, there must have been an identification, anyway.

Hazard

There had been an identification of 3C48 with what they thought was a star with some wisps and so on coming out of it.

Sullivan

Was that the basis of the identification, I guess? The wisps? There must have been many other stars in the field, too.

Hazard

It was just that it was a small angular size object, you see. It was less than a second of arc. You remember that what happened was that the motivation for going to very long baseline interferometry at Jodrell at that particular time was that if objects are like Cygnus A and so on with separations of the order of 30 seconds of arc and redshifts of round about 0.1 or a bit less, that if one started to look, then one could see the same objects out to redshifts of round about 2 and if you on the evolutionary models were going to have a minimum in the angular size distribution at redshifts round about 1, which actually for a thing like Cygnus A was the order that of a few seconds of arc. And therefore on that sort of theory if objects were like Cygnus there were going to be no sources less than a few seconds of arc. And in fact, what happened was Jodrell did find a few which had angular sizes of the order of a second or less than a second, a few seconds of arc. And then the occultations, you know, would have again would have showed the same thing it did show as soon as they started coming in. But most objects were in fact, are like this that we were turning up. You know, the first half dozen we did all looked the same, well, the first several of them. So that when you found things that were less than a second or so of arc it was reasonable at that particular time to think they might, in fact, be stars and not galaxies. So the positions were getting a little bit better but not all that much better. And so when they looked at the positions of these small angular size ones, at one or two of them, and they found a star particularly in 3C48 with possibly some wisps. Maybe the wisps made it look different.

Sullivan

So this was going back to the radio star idea temporarily anyway?

Hazard

Yes, I think so. And I think there was talk then that finally radio stars had been found. But, of course, what would have happened if 3C273 hadn't come along. I don't know. You see, Greenstein is the one that got spectra of 3C48 but he couldn't interpret them. And the idea that they were high redshift ones had not entered their heads of course because they were so unusual altogether. Now whether the thing would have stood around for a few years with nobody getting anywhere or not is a bit difficult to tell or whether somebody would have come up with the answer anyhow. But the chances of anybody saying that this Mg II or something or other lines would have been quite small. And in fact you see there was no object turned up with the Balmer lines for a very long time again. We have another one now with a lower redshift than 3C273. But you see you have to be less than .15. You know, once you get to what- you can't go very high before you start to lose things. So you really needed one clear-cut case with the Balmer lines to link you on to the other things before you could really get underway. I mean, you could have jumped the whole gap but I think it would have been a bit tricky to do it at that particular time. Maybe the N-galaxies led on to it. It might have come around some other way or maybe people would have pushed from the Seyfert galaxies that we know perhaps. I think the whole thing could have gotten into a mess otherwise. That came at a very fortunate time. And in fact before all this stuff had really even gotten underway, the solution was provided. It could have got a bit messy.

Sullivan

You just happened to have the right object at the right...

Hazard

Yes, the observations could have been coming at a very bad time actually. If the key hadn't arrived bang on time which it did, such as I suppose is again might have caused consternation if pulsars had arrived at the wrong time. But they did, in fact, arrive at a sort of time when... [Sullivan: neutron stars, collapsed objects, etc. were being discussed.]

Sullivan

Yes, it often happens when the time is right for something, it seems to materialize.

Hazard

Yes.

End of Tape 18B

Sullivan Tape 19A

Sullivan

Ok, this is continuing with Cyril Hazard on 20 March ’73. Along this same general line what about the cooperation between optical astronomy and radio astronomers? In the early ‘50s there was only [Walter] Baade and [Bart J.] Bok...

Hazard

Minkowski, I think. Minkowski was, in fact, the only one I knew really. In fact, I think probably Minkowski was probably the more important one.

Sullivan

Was this because the optical astronomers just didn't understand anything about what was going on or they just didn't see its importance?

Hazard

I think they probably didn't see its importance. Well, I think there were probably several things. I think the positions were so atrocious that were being provided.

Sullivan

So they couldn't be bothered?

Hazard

Well, that's right, it was a long time even after QSOs. It was a pretty time-consuming job for them if you were giving them bad positions when they're getting such a small amount of time on the big telescopes. And Minkowski and Baade, of course, got into the act with the- when the reasonably accurate positions came along for Cygnus and Cassiopeia. It strikes me that maybe because Baade died not all that long afterwards. But Minkowski seemed to play a bigger part in it round about that time. And certainly he was the only one that I knew, that I’d met around that time, apart from [Jan Hendrik] Oort, of course, but that was along different lines.

Sullivan

Who?

Hazard

Oort.

Sullivan

And Bok is also another...

Hazard

Yeah, but I think it was just that fact that radio people really didn't have the data to contribute at that particular time. And it was only when really accurate positions started to come along. There were people like [David W.] Dewhirst and so on that were doing something, you know, in the later stages Dewhirst. Once sources were coming along I think that they were trying to identify things. And a lot of the stuff they did was right, like the fact that they were saying there were elliptical galaxies in those places and so on. So that I think the radio galaxies were getting reasonably well understood. But I don't think that one can... I think the time really wasn't right for the optical cooperation until the radio techniques themselves, by themselves, had developed as a subject by itself, until the technical competence and had started to contribute. And I think as soon as that happened that really what happened was that not only did the optical people come in, but the evolution of people you know. Radio astronomy really started to begin ceasing to be a separate compartment. It started to move into the mainstream of astronomy. It has been already on the line work and so on but in the ordinary extragalactic stuff started to move into the thing. And then I think that the people began to change.

Sullivan

You think the hydrogen line work was more into the mainstream of astronomy earlier than the radio source?

Hazard

Oh, I think so because I mean in the sense that the theoreticians and optical astronomers are people who are experienced in optical astronomy, took part in it from the beginning. It's required that people who understood the Galaxy and so on to take part in it. That was probably a fairly fortunate development the way that particular one occurred here [Sullivan: Holland]. And I think people like Bok and Oort and so on came into it because- well, although I mean there were things being done by [Gart] Westerhout and so on, were tackling the source distribution and so on, as to the significance of those. But again in terms of the fact that they were in the Galaxy. But when it was accepted they were outside the Galaxy I'm absolutely certain, I wouldn't even be surprised actually if the first categorical statement backed up by some evidence isn't in the paper that I put in Observatory. It's not a paper, it's a summary of a conference at Jodrell.

Sullivan

Is this the meeting in '55?

Hazard

It must have been around '54 or '55. Now I was absolutely convinced they were extragalactic by '52 or '53. A long time before it was moving that way. Certainly by '53.

Sullivan

But there was a great debate going on.

Hazard

Sure, there was a great debate going on, and Ryle and so on was in the forefront of them being galactic. I certainly wrote in my thesis in '54. I must have had the ideas dated back to '53. And I was categorical they were extragalactic by then. [Thomas] Gold had been suggesting it already at the Solvay Conference and so on in London. And in fact in looking back, the arguments that Gold and [Fred] Hoyle and so on were producing at that time were pretty convincing except that people didn't listen to them, I don't think that although you needed to up the contributions over normal galaxies by a big amount, it was really a much smaller figure than you needed to up things over the stars. But again the evidence wasn't there at the time.

Sullivan

It was only a sort of plausibility?

Hazard

Yes. I'd done calculations on the thing in my thesis and from some of them showed it could explain everything fairly straightforwardly if they were extragalactic with the same sort of density. In fact, you gave them some sort of dispersion. And I think by that time there must have been - you know, it's very difficult to tell.

Sullivan

I suppose another point is that there was, of course a much longer tradition in astronomy on galactic astronomy. Extragalactic astronomy was a relatively new field.

Hazard

It was comparatively new, really.

Sullivan

There was not much was known about it, so that all the radio people were working in extragalactic and it was very hard to see the tie-in whereas there was a sufficient background in the galactic optical astronomy that they could see how it fit in there.

Hazard

I think that's possibly true. I think it may be of course that possibly it's because radio astronomy got underway in England and here [Sullivan: Holland] and in Australia. And the only people who knew any extragalactic astronomy were in the States.

Sullivan

Well, that's an interesting point, too.

Hazard

It may have been that if, in fact, it got underway in the States more easily it might have been very much different. It might have been very much different if [John G.] Bolton had actually started off his radio astronomy career in California and not in Sydney and the first stuff had been dealt with in California. It's possible that people might have- who were interested in extragalactic- looked on the things as extragalactic from the beginning. You can't tell.

Sullivan

There were a couple of early groups but they were not in California. They were in the East Coast.

Hazard

Yes, and they didn't do a great...

Sullivan

They didn't do extragalactic work. They worked on the sun and the moon and planets.

Hazard

That's right. But it's possible, you see, that if somebody had been doing these source surveys and had, in fact, been talking all the time with extragalactic people that these possibilities might have come more to the fore, I suppose. I mean that's possible, you can't tell.

Sullivan

Yes, that makes sense.

Hazard

It's quite right, I suppose. And in that particular sense it may have been that I was particularly inclined to have an extragalactic in that I'd done all my work on extragalactic stuff almost from the beginning on normal galaxies.

Sullivan

Well, so it was sort of natural?

Hazard

Yes.

Sullivan

One tends to make the data fit his area of expertise?

Hazard

That's right. At least you're not frightened of it, anyhow. You have some familiarity with the terms and so on, at least.

Sullivan

Ok, let's go back to just coming back from Australia. Then what did you work on, what was going on at Jodrell Bank?

Hazard

I didn't go to Jodrell Bank. I went to Arecibo then.

Sullivan

You went to Arecibo, ok. And this is what year now?

Hazard

I went to Australia in the end of 1960, I think, and left Australia in '63, I suppose, the end of '63 something like that and went to Arecibo while they were just getting underway. And it happened that there was an occultation of 3C273 occurring there about three weeks after I arrived.

Sullivan

And the dish was operational?

Hazard

The dish was operational but we had nothing up there to do it with. We wanted to really have a bash at it, a really good small angular size measurement. And for that we didn't want to use the whole dish. And so I built a multi-frequency feed. A feed in fact which for survived for several years after. We put it together in about a week and it worked very well. We turned out resolutions down to about 0.1 second. We got the observations at 40 megacycles. It was certainly by far the only time it got down to about 10 seconds of arc resolution at 40 megacycles. And then we started development for occultations and did quite a lot. But we were more interested in, I suppose at that particular time, in the theory of the stuff in many ways. Although I’ll tell you what did happen then, once we got the first occultations they were small ones. The fact that you could use the doubles, I suggested that then the doubles were the right way to do the angular size measurements. That was fairly obvious right from the beginning.

Sullivan

I don't see exactly...

Hazard

The idea of that particular one was to do cosmology by measuring angular sizes. They were trying to do it at Jodrell.

Sullivan

Oh, to use the separation of doubles?

Hazard

The separation of doubles and that was something I suggested doing. And, in fact, a lot of this stuff that I did round about then is was only being repeated then. But it turned out it was presented in the Fourth Texas Symposium of which the proceedings never appeared. Something in the CSIR report and I forgot about it for a couple of years. So they all thought this other thing was going to come out, but it never appeared since then. But a lot of the stuff was the structures of QSOs and so on, it's in there, which has only reappeared in the last few years. That was about 1967. And then we were trying to develop new feeds, trying to look at spectra and measure positions and so on. We were doing that for about 18 months and then I moved up to Ithaca.

Sullivan

What was the main astronomical purpose for the Arecibo dish?

Hazard

Oh, Arecibo was built originally to do back-scatter measurements by Bill [William E.] Gordon on the ionosphere.

Sullivan

Right, but with no astronomy in mind at that time?

Hazard

Not really. Well, yes, radar astronomy because there was obvious interest in doing radar of the planets beyond the moon and so on. And, of course, a lot of time was and is still devoted to that. But I don't think there was any great thought given to astronomy. Obviously there wasn't because nobody who was going to build an astronomical facility would cut it off at 38° when Andromeda was 2° or 3° further north. Obviously you'd make sure you got Andromeda in. So it was fairly obviously, I think that there wasn't a great deal of thought at that particular time given to the...

Sullivan

Well, how did this change? Or was there someone...

Hazard

I don't know exactly how it changed. In other words there was a political upheaval round about that time. I don't want to discuss the wrongs or the rights of it all, because actually I wasn't there at the time. I just arrived at the tail end of this, which ended with Booker leaving Cornell and Bill Gordon and so on, and Tommy Gold and them. And so presumably the idea of moving it over to astronomy was basically derived with Gold as Professor of Astronomy and so on in Ithaca. I presume that that was what, but I don't know. Marshall Cohen was there, he was down there. And so there were a few people tending to do astronomy. They'd already done one or two occultations, I think. [Mukul Ranjan] Kundu was there. There were a few people doing it, but obviously I don't think they had any say in the building of the thing in the beginning. It was an electrical engineering project to begin with. Again, that's fairly obvious in that the whole of the effort in which you know, in some ways held back the development of the facilities as a radio astronomical thing, was predicated on the fact that one wanted a feed which would feed the whole dish high powered two polarization. I mean now that people have gone over to building single-polarization feeds to feed 500 or 600 feet of the dish for radio astronomy the thing worked perfectly. They could probably have been developed earlier on, I think. I would guess if that had been tackled. There was no particular use made until the last few months. You know, I started it several years ago and its only got going now and we're doing it now to use the multiple-beaming facility.

Sullivan

At Arecibo?

Hazard

About 10 overlapping beams where you can do surveys very quickly. So all that sort of thing hadn't really been developed. It has only really come into operation now and, of course, I supposed now that they're upgrading the dish which was my original motivation for going to multi-beaming in many ways, to try and get over the fact that you wouldn't be able to track accurately enough. That looks very promising. And, of course, Arecibo was given a very big boost then again by pulsars. Not simply because but to a large extent because it had already been recording and was available for radar work. It was just set up perfectly for this.

Sullivan

It had a great sensitivity at low frequencies?

Hazard

Yes. But even more than that I think, it had all the equipment there, used for radar work.

Sullivan

For timing and so forth?

Hazard

For timing and recording everything, rapid recording and timing, everything was there. And so it was really ideally placed for this. And they didn't need the resolution, they didn't need the tracking accuracy and so everything was pretty well set-up for that.

Sullivan

Well, I don't want to go beyond there. I’m going to cut this thing off sometime around ’65...

Hazard

It gets out of hand after that, yes.

Sullivan

But is there anything else...

Hazard

I think the point about the mid-1960s is fairly important simply because possibly slightly before that and round about that time there was a very important change occurring, I think, in radio astronomers as such, I mean certain groups of radio astronomers. I think that the people who are really working on things like QSOs and so on are starting in many ways to diverge from the ordinary radio astronomical things. They're becoming more astronomers and not radio astronomers anymore. I think they're becoming more interested in the optical work, working with the optical observers. It's obvious that the radio itself is only a very small part of the whole thing. Plus on top of that, the instruments are reaching such a point that you're not building them anymore and a lot of the pleasure of doing radio astronomy is gone. You don't have any particular satisfaction in going and pressing buttons on some instruments.

Sullivan

As you know you cannot press buttons at a place like Westerbork.

Hazard

That's right. So that nearly all of the interests that used to exist in radio astronomy of going and building receivers and building antennae and connecting it up and making it work and seeing the sources come through. And that in itself being an achievement apart from anything else. And then you could write the thing and say that these were the positions of the sources. In fact, that was an achievement in those days. You didn't have to do any astronomy as such afterwards to justify it. But now you can't- people do, I think, but I don't see how anyone can take any credit for going to any instrument now and measuring the flux of so many sources or measuring the positions of so many sources. It doesn't strike me that that's a contribution whatsoever.

Sullivan

Right, you've got to interpret it.

Hazard

Yes, and so people have got to become much more problem oriented. And I think this sort of thing was starting to take place in the 1960s.

Sullivan

I hear you, but don't you think it happens simultaneously with the largeness of the facilities? Like you say, one person could not build it and still be able to do the astronomy.

Hazard

It's happened simultaneously with that, but it's also happening, I think, with the significance of the results that are coming out. I think that while you had a set of unidentified radio sources and one could play about with cosmology and so, then this was a radio astronomical problem as such. It could reach certain conclusions that might or might not be right but you only needed the radio data and you had very little else to go on except in a general sort of way. Once you reached a quasar sort of stage and so on, then the objects that you were finding had great intrinsic importance. The investigation was only beginning with the radio investigation. And I think if you worked in those sort of fields you began to get resentful, really. And felt that it was silly that you were cut off from the further development to a certain extent. So to appreciate - once you'd found quasars or once you'd found pulsars, any of those things, to really appreciate even what you'd done or to get the full satisfaction from it, you really had to go a lot further. You had to start to understand the optical stuff and you had to take part in it. You had to start to understand the implications of it and if you were doing pulsars no doubt you wanted to understand all about neutron stars and so on. So the only thing was developing away from radio astronomy. So perhaps you're right. Maybe that's the point to stop because radio astronomy is a subject you could almost argue begins to cease to exist at that time.

Sullivan

Yes, well, I can think of another way of putting it is that it becomes less and less engineering and more and more science.

Hazard

Yes.

Sullivan

Because from what you've said the great part of the joy was in the engineering part.

Hazard

Yes. It was. Building a receiver which would do it and getting it out.

Sullivan

Whereas someone like me...

Hazard

Building an antenna or something...

Sullivan

Right. You don’t even think about building an antenna these days.

Hazard

It was interesting to get out with the wires and soldering irons and concrete mixers. You enjoyed it. You have to do something else now. There's no difference in using Westerbork to using an optical telescope. Nothing much different you do with the results when you've got them.

Sullivan

That's true.

Hazard

So it's silly to say you’re an optical astronomer, you might as well call yourself a blue-plate astronomer or a red-plate astronomer.

Sullivan

That's a very good point.

Hazard

So it might be that the mid-1960s were sort of the time that radio astronomy became of age and just became a part of astronomy, I suppose, which is a good thing.

Sullivan

Ok, well thank you very much. That finishes the interview with Cyril Hazard on 20 March 1973 at Groningen.